When I put a decent throttle and generate boost the engine misfires. I can lay off the throttle slightly and the misfire will subside and I do not throw any OBD2 codes. Today I removed the S/C belt as a test and under full throttle, to red line, there was no misfire. I recently replaced the plugs with AC Delco 41-101 and last year I replaced the fuel pump with a Airtex E3535M fuel pump and fuel filter at the same time.

If I am only misfiring under boosted conditions I suspect either a lean condition (fuel pump not keeping up), possibly the fuel filter (only a year old) or maybe even spark plug wires. I am just baffled that without the S/C belt (running without boost) there is no misfire under full throttle...car ran fine.

Did you ever figure this out i have the same problem and have tryed everything i can think of. I dont know what else to try?

Do you have a way to scan the computer for a missfire per cylinder.. most hand held scanners will do it, might check into an App for your smart phone and a blue tooth OBDII dongle (like $25 on ebay).

If you can scan it you will have a Misfire count per cylinder and you will know where to start.. Bad Plug (i had one cracked out of the box) bad plug wire, Bad ignition coil, Bad Ignition control Module (ICM). Mine had a miss when under a load/boost and NEVER showed a missfire code, but when i scanned it with my tuning software it did report that my Cyl #3 was missing alot.. found hairline crack in the porcelain of the plug. replaced the plug and fixed my problem in my case..

Just a thought, observe the engine while idling in a very dark garage. Use your hand to operate the butterfly on the throttle body and see if there might be any "stray" ignition spark under the hood. Probably not the cause, but you'd be amazed at what you discover doing this sometimes. - BC

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